Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2000-08-31
2004-01-13
Jaworski, Francis J. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C600S491000, C073S001570
Reexamination Certificate
active
06676600
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to the field of medical instrumentation, specifically the use of electronic storage devices for storing and retrieving data relating to, inter alia, particular instruments or patients.
2. Description of Related Technology
The ability to readily measure various physiologic parameters associated with a living subject, such as arterial blood pressure or ECG, is often critical to providing effective care to such subjects. Typically, under the prior art, measurement of such parameters is accomplished using a system comprising a host device such as a portable or semi-portable monitoring station that is used in conjunction with a replaceable/disposable probe or sensor assembly, the latter being in direct contact with the subject and measuring the physical parameter (or related parameters) of interest. Such replaceable and disposable sensor assemblies are highly desirable from the standpoint that the risk of transfer of bacterial or other contamination from one patient to the next is significantly mitigated; the portion of the sensor assembly (or for that matter entire assembly) in contact with a given subject is replaced before use on another subject.
However, despite the mitigated risk of contamination, the use of such prior art disposable sensors also includes certain risks. One such risk relates to the potential re- use of what are meant to be single-use only components. Inherently, individuals or health care providers may attempt to re-use such single use components if there is no seeming degradation of the component or perceived threat of contamination. However, in the case of certain devices, the degradation of the component may be insidious and not immediately perceptible to the user. For example, the offset (i.e., difference of voltage generated by the device at certain prescribed conditions) associated with an elastomer-coated pressure transducer used in a non-invasive blood pressure monitoring device may change progressively in small increments over time due to swelling of the elastomer coating resulting from exposure to certain chemical substances. This variation in offset manifests itself as a change in the ultimate blood pressure reading obtained using the device, thereby reducing its accuracy. Hence, the readings obtained using the instrument may appear to be reasonable or correct, but in fact will incorporate increasing amounts of error from the true value of the parameter, which may significantly impact the treatment ultimately provided to the subject. Hence, what is needed is an approach wherein any such degradable or single use components are reliably replaced at the necessary interval such that performance does not appreciably degrade.
A related issue concerns the re-use of such devices on different patients. Specifically, if the “single use” components are perceived by the user not to degrade rapidly, the user may be tempted to use the device (including the single use transducer(s)) on several different patients. Aside from the aforementioned performance issues, such repeated use may be hazardous from a contamination standpoint, as previously discussed. Ideally, portions of the device capable of transmitting bacterial, viral, or other deleterious agents are disposed of and replaced prior to use on another patient.
Another risk concerns the use of third party or non-compliant sensors with the host device of the original equipment manufacturer (OEM). While such third party sensors may ostensibly be manufactured to the design specifications and requirements of the OEM, in many cases they are not, which can result in readings obtained using the system which are less than accurate or even wholly non-representative of the parameter being measured. Even OEM supplied disposable sensors may have defects. Another troubling aspect is the fact that the caregiver or health care professional who is provided with such disposable sensors may have no means by which to verify the quality or acceptability of a given replaceable sensor, and therefore the accuracy of any reading they may obtain using that sensor may be called into question. Hence, even if the majority of sensors within a given lot obtained from the third party manufacturer are acceptable in terms of performance, the caregiver often has no way of knowing whether the next replacement sensor they use will perform as designed or intended by the OEM and yield representative results. In the ideal case, the quality of each individual replacement sensor would be determined by the host system prior to use (such as when the new replacement sensor is first installed on the host), and the caregiver apprised of the results of this determination.
The calibration of the replaceable/disposable sensor, whether OEM or otherwise, and the host system must also be considered. Under the prior art approach, calibration is most often performed on the system as a whole at a discrete point in time, and is generally not performed before each use of the device after a new sensor or probe has been installed. Hence, the calibration of the host system and replaceable sensor as a whole is not specific to each given sensor, but rather to a “nominal” sensor (i.e., the one in place in the system when the calibration was performed). For example, the system may be calibrated before first use, and then periodically thereafter at predetermined intervals, or at the occurrence of a given condition. Under this approach, changes in the physical operating characteristics of the host system may result in changes in the calibration over time. Due to any number of intrinsic or external factors, the device may “drift” between calibrations, such that a reading taken with the device immediately following calibration may be substantially different from that obtained using the same device and identical conditions immediately before the next calibration.
Additionally, due to manufacturing tolerances and variations, the performance of each individual replaceable sensor may vary significantly from other similar devices, as previously described. Such variations are generally accounted for by the OEM by specifying a maximum allowable tolerances or variances for certain critical parameters associated with the sensors; if these tolerances/variances are met for a given replaceable sensor, then the accuracy of the system as a whole will fall within a certain (acceptable) tolerance as well. Ideally, however, the system would be calibrated specifically to each individual replaceable sensor immediately prior to use, a capability which is not present in prior art disposable medical devices.
Another concern relates to the potential for surreptitious alteration of data stored by an instrument prior to or during operation. As with many other types of devices, the ability to make a device “tamperproof” is of significant importance, in that this provides the caregiver and subject with additional assurance that the disposable sensor in use is the correct type of sensor for the host system, that the sensor assembly and host system are properly calibrated, and that the disposable sensor has not been used on other subjects.
Lastly, it is recognized that prior art measurement systems do not include the facility for evaluating the accuracy of a given measurement or host/sensor combination after readings have been taken. Many systems are capable of storing data relating to a measurement obtained from a subject in terms of the estimated value(s) derived by the system, yet none of which the Assignee hereof is aware allow for the retrieval of data specific to a given sensor or permit the system operator to evaluate the performance (and accuracy) of the system historically. Such information is of great potential utility in the medical field, especially with relation to medical malpractice litigation, by enabling the caregiver or OEM to reconstruct the operation of their equipment to demonstrate that a given measurement obtained using a given sensor and host unit was in fact accurate, that the disposable sensor had
Conero Ronald S.
Gallant Stuart L.
Gazdzinski & Associates
Jaworski Francis J.
Tensys Medical, Inc.
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